Flotation apparatus



W. O. BORCHERDT.

FLOTAHON APPARATUS.

APPLICATION FILED JAN. 24. UN].

Patented Deb. 30,1919.

momma fecting the flotation is introduced through WALTER 0. BORCHERDT, OF AU STINVILLE, VIRGINIA, ASSIGNOR TO THE NEW JERSEY ZINC COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

FLOTATION APPARATUS.

Specification of Letters Patent.

Patented Dec. 30, 1919.

Application filed January 24, 1917. Serial No. 144,121.

To all whom it may concern:

Be it known that I, WALTER 0. Bononnunr, a: citizen of the United States, and a resident of Austinville, in the county of \Vythe and State of Virginia, have invented certain new and useful Improvements in Flotation Apparatus; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appcrtains to make and use the same.

This invention relates to a flotation cell or apparatus of the type used in the socalled sub-aeration system of flotation, in which the air or other gaseous ,fiuid for efthe porous bottom of the flotation cell. The

invention comprises such a cell or apparatus.

in which the" top surface of a porous diaphragm is provided with a layer of metallic spherules, through which, and from the .uppersurface of which, the air enters the flotation cell.

In the" various porous mediums used in flotation cells of the sub-aeration type, a very considerable -res1stance'1s offered to the passage of the air therethrough. In order to subdivide the air to the required extent, and in order to .securethe necessary uniformity of the air-entering the cell, as much as 80 to 90% ofthe-tota'l air pressure consumed in the porous medium. So also, there is a tendency with the porous bottoms commonly used to become clogged either with impurities filtered out from the'air or with ore pulp which settles to the bottom of the cell or to become incrusted by deposited salts. With cloth bottoms, even where several plies of cloth are stitched together every half inch each way, there is a tendency toward unevenness in the air supply introduced because of unevcnnesscs in the surface of'the cloth due to bulging or puckering.

It is an object of to overcome or minimize such disadvantages of flotation cells provided with porous bottoms" of the nature referred to.

According to the present invention, the

bottom of the cell, above the compressed air chambers, is provided with a porous dia phragm serving as a support, and with .a layer of metallic spherules above the diaphragm and supported thereby for .efiecting the more even distribution. of the air bubbles.

The porous diaphragm which serves as the present invention the support for the layer of metallic spherules may be made of any suitable porous material, such as tile or cloth, which in itself would be capable of producing an even or uniform discharge of fine air bubbles. 'lhat 1s, cells of the type commonly constructed can be provided with a layer of metallic spherules upon the upper surface of the porous diaphragm, and the added advantages due to such added layer will be obtalned. The invention is thus capable of bemg applied to cells already constructed and provided with porous bottoms which in themselves would give a uniform discharge offine air'bubbles. The added layerof metallic spherules on such porous medium would have the advantage of giving a more uniform discharge of air bubbles, since the effect of rivets, rods, etc., which are employed to hold these various types of porous bottoms in place and which cause more or less running together of the fine air bubbles emitted in their vicinity, would be done away with. Such anamalgamation of many fine bubbles into fewer, coarse ones is objectionable in a flotation cell.

So, also, in the case of cloth bottoms, such as those which are commonly used in cells of the sub-aeratio type, one of the chief difficultiesencount red is to hold the cloth down smoothly against the pressure of airbeneath it. It will be evident that, to secure a uniform disengagement of -fine bubbles, the cloth should be a'perfect plane free from projections of any kind on its upper surface. It practice, this is a condition diflicult or impossible of attainment, since, even when stitched down at intervals of one-half inch will bev equally evident that, in

der the influence of the pressure beneath, tends to pucker'up or bulge, with the result that the disengagement of air bubbles is concentrated at the points of these packers or bulges, instead of being uniform. An added layer of shot or other metallic spherules overcmncs these disadvantages or defects of such a cloth bottom and results, as above pointed out, in more uniform discharge of the air bubbles.

While the layer of metallic spherules can porous media which in thembe applied to glvmg a fairly even selves are capable of and uniform discharge of hue air bubbles, such porous media are, by the addition of the added layer of metallic spherules, no

port the layer of metallic spherules and" give to the an passing through it a prelimi nar sub-division sufiicient to enable the me-- tallic spherules to further subdivide the air to the required extent.

The invention i illustrated in the accomused in the so-called sub-aeration system of flotation, withcertain embodiments of the invention illustrated in connection therewith. Inthe accompanying drawings, Figure 1 shows a flotation cell 111 vertical longitudinal section; Fig. 2 is an enlarged view showing the construction of the cell bottom; Fig. v

3 shows a modified form of porous diaphragm; and Fig. a shows a still further modification of the invention.

The cell 1 is of the general type used in the so-called sub-aeration system of flotation; but is provided with a level or horizontal bottom instead of a sloping or inclined bottom. This cell is provided with the inlet eonnection 2 leading to the inlet compartment 3, which is separated from the main portion of the cell by the partition 4 so that the pulp enters the main portion of the cell below this partition at 5. The froth overflow level is indicated at 6 and the launder into which the froth overflows at 7 the froth escaping from the launder at the outlet 8.

The cell is provided with the bottom 9 above which are the series of con'ipressed air compartments formed by the supporting partitions l0 and the porous diaphragms 11 above which is the layer of metallic spherules 12. In order to overcome the tend-- ency of the spherules to travel with the pulp and be discharged from the apparatus, transverse strips or battens or partitions 13 are provided, suitably secured in place, and extending somewhat above the upper surface of the layers of metallic spherules. The transverse strips or battens 13 extend crosswise of the cell and are etfcctivcin preventing a migration of the splicrules lengthwise of the cell, or in other words, these transverse strips prevent longitudinal movement of the metallic spherules. The batten 13 which is nearest the tailings discharge 16 may be made somewhat higher than the others 86 to prevent the final discharge of the mepanying drawings showing a cell of the type tended to act only as a plane or level surtallic spherules with the tailings. Each of the series of compressed air compartments is provided with an inlet 14 for connection with the compressed air supply and above each inlet is arranged a bafile 15 for spreading out the entering air current. Fig. 2 shows more in detail the construction of such a bottom as that of Fig. 1. From this figure, it will. be seen that the porous supporting diaphragm 11* is made up of a lower and coarser screen 17 covered with a fine screen 18 which in turn may be provided with a covering of cloth 19,.as indicated in Fig. 3, in which 11 designates a thus modified supporting diaphragm.

In practice, I have used a coarse screen cloth over which was laid a finen cloth of about 30 mesh, the openings in which were larger than the particles of ore to be fed to the cell but smaller than the metallic spherules to be used. The fine screen cloth can be stitched to the coarse cloth with fine wire or soldered at intervals to'hold. it in position, or the screens may be otherwise secured and held in place in the flotation 90 cell. Such a combination of screens, by itself, would be incapable of producing a uniform discharge. of fine bubbles. It is not, in fact, intended for this purpose but is inface to support the layer of metallic sphcrules which are held in place longitudinally by the transverse strips or battens which cross the cell at intervals.

The shallow box-like spaces or compartment-s thus formed by the porous diaphragm and the transverse strips or battens are partially filled with metallic spherules to a uniform depth, the depth of the metallic spherules and the fineness of the metallic spherules depending upon the desired fineness of the air bubbles to be produced.

' As the size of the bubbles is determined by the character of the surface from which they deliver, rather than by the mass of the porous medium, coarser bubbles can be obtained by using coarser metallic spherules, and finer bubbles by using finer metallic spherules. Thus,'with some ores, galena seems to float in preference to blcnde if a coarse froth is obtained, and vice versa.

The nature of the oil used will, of course,

largely affect the result in such cases, but the tendency of a finer or coarser froth formation due to the finer or coarser air we bubbles formed, tends to reinforce the action of the oil in such cases.

Whereas, with cells such as heretofore commonly constructed, it has been the practice where fine bubbles were desired'either to use a number of layers of fine grain cloth, or a fine grain tile, with resulting increased resistance to the passage of air and accompanying higher pressures of air and loss of power; w th the present invention it is possible to obtain either a finer or coarser bubble formation with materially reduced resistance to the passage of the air and resulting material economy in the power required. This follows from the fact that the character of the bubbles is determined by the .final surface of disengagement, and from the further fact that a layer of finer metallic spherules on a coarse porous supporting medium would give a delivery of fine bubbles while retaining the advantage of low resistance to the passage of air through the coarse porous medium and through the layer of metallic spherules itself.

Furthermore, since the metallic spherules, during the passage of the air, tend to keep in constant slight relative movement, the bottom is less likely to retain and be clogged by any particles of ore and ore gangue or by impurities in the air or water supply than a porous medium in which the relative positions ofthe various parts are fixed. The bottom thus becomes whatmay be called a self-cleaning bottom, one advantage of which being that the use of impure air is ,less important than in the case of a stationary porous medium which would act as a filter and tend to become clogged by the accumulated impurities.

The advantages of the present invention, with respectto the self-cleaning nature of the metallic spherules bottom, are also obtained when it is used in combination with other porous medium, so far as the ore or gangue is concerned. That is to say, whether the layer of metallic spherules be supported by a relatively coarse supporting medium, or by some other porous medium, the bottom is less likely to retain and be clogged by any particles of ore or gangue than in cases where the ore and gangue come directly in contact with a rigid pore ous medium through 'whiehthe air is introduced into the flotation tank.

Fig. 4 shows a porous silica tile 11 in combination with a layer of metallic spherules supported thereby. Such a bottom may be one which in itself is capable of giving a uniform supply of air to the cell or it may be one which is too coarse for this purpose. Coarser tiles, as well as coarser cloth, offer less resistance to the passage of the air. but give correspondingly coarser bubbles. They also permit the penetration and clogging of the material Withore slime when used by themselves as the porous media in flotation cells. However, by adding a layer of fine metallic spherules, a fine bubble emission can be obtained, and penetration of the slimes substantially prevented, While, nevertheless, most of the advantages of lower resistance are retained-L Accordingly, by adding a layer of metallic spherules' to a coarse cloth or tile bottom, a finer air bubble supply can be obtained; while the sizeof the air bubbles is capable of ready varia ion by replacing the layer of metallic spherules with a finer or coarser layer, depending upon the desired result. 3

It is further possible, by using mixtures of metallic spherules of different sizes, to obtain a less uniform disengagement 0t a r vary with the nature of the supporting diaphragm and with the results desired.

It seems to be an advantage in some cases to prevent too low resistance of the layer of metallic spherules or shot and its supporting diaphragm to the passage of the air therethrough. Increasing the depth of the layer of metallic spherules or shot tends slightly to increase this resistance as does also the addition of a layer of cloth between the fine screen and metallic spherules or shot, as indicated in Fig. 3, or the use of finer screen cloth, or of twilled metal filter cloth between the coarse screen and metallic spherules or shot. The added weight of the metallic spherules or shot above the porous diaphragm tends to weigh down the diaphragm so that the present methods of stitching or riveting or gm'dding, become less important.

\Vhile in the drawing the metallic spherules 01' shot have been shown as somewhat separated, for purposes of illustration, it will be understood that they form a continuous layer in practice above the supporting diaphragm, whether this diaphragm be merely a support or whether it be in itself capable of giving auniform bubble disengagement such 'as is obtained with cloth or tiled bottoms now commonly used.

.Iti is one object of the invention, when screens are used for the supporting diaphragm, that no organic matter enters into the construction of the porous bottom. Such bottoms have the advantage of being selfcleaning, and the screens can be coarser than the ore fed onto the machine so that there is a Very material reduction in'the air pressure required with resulting economy in the power required for the air compression.

The metallic spherules or shot may be of lead or of other suitable material. With lead shot, the Weight of the shot. is such that even discharge of air through the bottom so intense that water vvas removed from the cell, has been found not to disturb the surface of the shot materially, or to cause the shot to be carried over any of the battens. The air supol which would be used in practicc, would. of cours be much less intense, and, accordinglv. the shot can be relied upon to stay in place except for the tendency to continual sli ht relative movement, during the normal operation of the flotation cell. It has also been found that the provision of the battens which extend somewhat above the surface of the shot does not injuriously retard the flow of the pulp through the apparatus.

I claim:

1. A flotation apparatus, comprising a series of shallow box-like comparti'nents, each of which has a porous bottom comprising a supporting diaphragm and a layer of metallic spherules supported thereby, means for introducing gaseous fluid through the diaphragm and layer of metallic spherules of each of said porous bottoms, and means for causing the ore pulp to be subjected to flotation treatment to flow longitudinally of said series of compartments so that the tailings are discharged at the end thereof and the ore particles are removed as an overflow froth; substantially as described.

2. A flotation apparatus provided with a porous bottom for the introduction of gaseous fluid, said porous bottom comprising a supporting diaphragm and a layer of metallic spherules supported thereby through which the gaseous fluid is introducedinto the apparatus, said metallic spherules being of such a character and so supported that they are kept in slight relative movement during the passage of the gaseous fluid therethrough thereby minimizing any tendency of the porous bottom to become clogged by particles of ore or the like; substantially as described.

3. A flotation apparatus having a porous supporting diaphragn'i, arranged to divide the apparatus into a main pulp-containing chamber and a bottom gaseous fluid compartment, a layer of metallic spherules sup ported by said diaphragm,.and means for introducing gaseous fluid through said diaphragm and layer of metallic spherules in such a manner that during the normal operation of said apparatus both the ore parti cles and tailings under treatment therein are forced away from said layer of metallic spherules; substantially as described.

4. A flotation apparatus provided with a porous bottom for the introduction of gaseous fluid, said porous bottom comprising a plurality of layers of fabric of progressively finer mesh and a layer of metallic spherules supported by the upper of said fabrics through which the gaseous fluid is introduced into the apparatus, said metallic spherules being of such a character and so supported that they are kept in constant slight relative movement during the passage of the gaseous fluid therethrough thereby minimizing any tendency of the porous bottom to become clogged by particles of ore or the like; substantially as described.

5. A flotation apparatus provided With a porous supporting diaphragm at its bottom, a layer of metallic spherules supported by such diaphragm, means for introducing gaseous fluid through such diaphragm and layer of metallic spherules in such a mannor that during the normal operation of said apparatus both the ore particles and tailings under treatment therein are forced away from the porous bottom, means for introducing ore pulp int such apparatus and for removing the tailings therefrom, and transverse strips arranged at intervals for holding the metallic spherules from longitudinal movement and for preventing their discharge with the tailings; substantially as described.

6. A flotation appa 'atus having a porous su )porting diaphragm arranged to divide the apparatus into a main pulp containing chamber and a bottom gaseous fluid compartment, a plurality of partitions dividing said gaseous fluid compartment into a plurality of independent sections, a gaseous fluid inlet at the bottom of each of said sections. a baflle arranged in each section above the air inlet thereof, and a layer of metallic spherules supported by said diaphragm; substantially as described.

7. A flotation apparatus having a porous supporting diaphragm arranged to divide the apparatus into a main pulp containing chamber and a bottom gaseous fluid compartment, a plurality of partitions dividing said gaseous fluid compartment into a. plurality of independent sections, a gaseous fluid inlet for each of said independent sections, a layer of metallic spherules supported by said diaphragm, and a plurality of transverse strips extending through and above said layer of metallic spherules for holding the spherules from longitudinal movement and for preventing their discharge with the tailings; substantially as described.

8. A flotation apparatus having a porous supporting diaphragm arrangedto divide the apparatus-into a main pulp containing chamber and a bottom gaseous fluid oompartment, a layer of metallic spherules supported by said diaphragm, and a. plurality of transverse strips extending through and above said layer of metallic spherules for holding the spherules from longitudinal movement and for preventing their discharge with the tailings; substantially as described.

In testimony whereof I affix my signature.

WALTER O. BORCHERDTL 

